We had a good one like that a while back. Essentially the code was like this (used to check client ID numbers)

sub is_integer {
    return 0 unless $_[0];
    return $_[0] =~ m/^\d$/ ? 1 : 0;
}
[download]

In development this routine was never required to deal with a TWO digit integer as all the developers used accounts with a <10 client ID number. Oh and the Test code.....the guy that wrote it tested all these args: undef,'', 'I am not an integer 42!', 0,1,2,3,4,5,6,7,8,9. Why ten tests for single digit integers and no tests for 16, 256,65535 GOK. Just goes to show that the volume of test is not the most important thing. Testing all the possible cases is. Even most of the probable cases would have been fine in this case.

So you can guess what happens. During a live demo client 10 gets created, but client ID 10 is not an integer according to the sub. End of that demo. Much egg on developer and manager faces. And the bug (besides the inadequate test suite) a single missing +

cheers

tachyon

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